Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!ames!hc!hi!cyrus
From: cyrus@hi.UUCP (Tait Cyrus)
Newsgroups: comp.sys.nsc.32k
Subject: GENIX compiler 'feature' (bug)
Message-ID: <12301@hi.UUCP>
Date: Thu, 30-Jul-87 13:27:19 EDT
Article-I.D.: hi.12301
Posted: Thu Jul 30 13:27:19 1987
Date-Received: Sat, 1-Aug-87 10:08:08 EDT
Organization: U. of New Mexico, Albuquerque
Lines: 34
Keywords: genix, c, compiler, bug


Here at UNM we are porting GENIX 4.2 to the nodes of a hypercube we are
building.  Currently we are 'playing' with ethernet code and ran, for
the second time, into a C compiler 'feature', although I would call it
a bug.

We have a structure which contains several other structures.  These
structures HAVE TO, because of the tcp/ip specs, be in certain places.
Well, the compiler appears to be quad aligning the different structures
within the outermost structure.

This is not the first time I have seen the GENIX C compiler generate
code where it aligned certain things on a quad boundry.  Why?  The
32xxx processor does not care where chars/words/ints/ptrs are, unlike
other machines.

Granted, if an int is NOT on a word/quad boundry, it will be slower
in execution, but it WILL work.

I guess my question is WHY is the GENIX 4.2 C compiler doing this and
is there a way to get it to NOT do this?

Thanks in advance,

-- 
    @__________@    W. Tait Cyrus   (505) 277-0806
   /|         /|    University of New Mexico
  / |        / |    Dept of EECE - Hypercube Project
 @__|_______@  |    Albuquerque, New Mexico 87131
 |  |       |  |
 |  |  hc   |  |    e-mail:
 |  @.......|..@       cyrus@hc.dspo.gov or
 | /        | /        seismo!unmvax!hi!cyrus
 @/_________@/